This invention relates to fluid pumps and more particularly to a centrifugal type of fluid pump. The invention also relates to fuel controls for gas turbine engines.
A problem with centrifugal impeller pumps, which operate during low flows, is the recirculation of flow from the collector thereof back into the impeller section. This flow recirculation contributes significantly to a reduction in pump efficiency and increases undesirable heating of the fluid being pumped.
Prior art devices which restrict the impeller discharge area or collector inlet area have demonstrated that a reduction in recirculating flow engenders a noticeable improvement in pump efficiency. However, the available mechanical systems in the prior art for controlling the inlet area on the collector do not allow for precise positioning of the valve which dictates the inlet area. Hence, the mechanical systems of the prior art which are employed to regulate the collector inlet area have not been adapted for the precise control to render them suitable for certain applications, such as aircraft applications.